Desreguladores endócrinos no meio ambiente: efeitos e conseqüências

There is an increasing interest in micropollutants in the environment that can interfere with the endocrine system, affecting health, growth and reproduction of animals and humans. These substances are known as Endocrine Disrupting Chemicals (EDCs) and can be found in domestic sewage, domestic wastewater treatment plant effluents, and in natural and potable waters. There are numerous chemicals classified as EDCs, such as pesticides, chemicals used and produced by chemical industries and natural and synthetic estrogens. EDCs can be related to the increase of the incidence of anomalies in the reproductive system of animals, cancer in humans and reduction of the masculine fertility.

Interferentes endócrinos no ambiente

Although the hypothesis that environmental chemicals may exhibit endocrine disrupting effects is not new, the issue has been a growing level of concern due to reports of increased incidences of endocrine-related disease in humans, including declining male fertility, and more significantly, to adverse physiological effects observed in wildlife where cause and effect relationships are more evident. The list of endocrine disrupting chemicals (EDCs) includes a range of anthropogenic compounds, phytoestrogens, naturally occurring sex steroids and synthetic estrogens. Within the aquatic environment, the presence of EDCs has concerned many scientists and water quality regulators. Discharge of effluents from treatment facilities is likely to be a significant source of input of contaminants to many systems, and the potential for concentration of hydrophilic compounds and transformation products within sludges has implications for their disposal. Then, understanding the processes and the fate of EDCs on the environment, as well as the mechanisms of endocrine disruption, may facilitate controlling or limiting exposure of both humans and the environment to these compounds.

Preparações e aplicações sintéticas recentes de enaminonas

Enaminones are beta-enamino carbonylic compounds bearing the conjugated system N-C=C-C=O, which makes them versatile ambident synthetic building blocks, particularly in synthesis of heterocycles. This review covers the last three years of the literature concerning the preparation and synthetic applications of enaminones.

Moottoripyörän rungon muuntelun valvontakriteerit muutoskatsastuksessa

Muutoskatsastusta koskeva lainsäädäntö aiheuttaa tulkintavaikeuksia ja rajoitteita moottoripyöräharrastajille ja alan toimijoille. Nykyinen asetus edellyttää tarvittaessa asiantuntijaselvitystä rakennemuutoksen lujuudesta ja hitsaustyöstä. Moottoripyörän geometria on laissa rajattu akselivälin ja emäputken kulman osalta. Moottoripyörien runkoja valmistetaan hitsaamalla seostamattomista teräksistä ja lämpökäsiteltävistä alumiini- ja terässeoksista. Runkojen muuntelu suoritetaan myös yleisesti hitsaamalla. Turvallisuuden kannalta tärkeiltä hitsausliitoksilta vaaditaan hyvää laatua, joka saavutetaan oikeilla hitsausparametreilla ja -suorituksella. Vaatimukset seostamattomalle teräkselle voidaan täyttää pätevöityneen hitsaajan toimesta. Lämpökäsiteltävät seokset vaativat lisäksi jälkilämpökäsittelyn, mikä edelleen vaikeuttaa runkojen hitsausta. Hitsien laadun merkitystä moottoripyörän rungossa tutkittiin soveltamalla rajoitetun vahingon periaatetta. Vauriotapauksena mallinnettiin satunnaisen rungon hitsausliitoksen murtuminen. Eri kuormitustilanteissa elementtimenetelmää hyödyntäen todettiin chopper-tyyppisten moottoripyörien runkojen olevan osittain vauriosietoisia ja havaittiin kriittiset hitsausliitokset emä- ja vaakaputken alueilla. Moottoripyörien runkojen kriittisiä hitsausliitoksia tarkasteltiin väsymisen kannalta. Soveltamalla tehollista lovijännitystä, vertailtiin emäputken hitsausliitosten väsymiskestävyyttä oletetulla kuormituksella. Tulosten perusteella muunneltu moottoripyörän runko voi olla alkuperäisrunkoa kestävämpi tai heikompi. Moottoripyörän akseliväli tai emäputken kulma eivät määrää kestävyyttä, vaan rakenteen yksityiskohtainen suunnittelu. Kriittisten liitosten väsymiskestävyyksissä havaittiin merkittäviä eroja eri mallien välillä.

Macrolactamas bioativas e síntese de macrociclos por reação de carbociclização radicalar mediada por hidreto de tri-n-butilestanho

This review presents natural, semi-synthetic and synthetic bioactive macrolactams and their structure-activity relationships when available. For macrolactams in clinical use the advantages and disadvantages in relation to other drugs are presented, and for synthetic macrolactams the method used in the cyclization is showed. Regarding macrocyclic synthesis by the tri-n-butyltin hydride-mediated radicalar carbocyclization reaction the precursor, the reaction conditions, products and yields, mechanism and cyclization mode are discussed.

Desenvolvimento e avaliação de um porta-amostra de baixo custo para caracterização elétrica de materiais cerâmicos

Conventional sample holder cells used to the electric characterization of ceramics at high temperature consists of an alumina tube and platinum wires and plates using a complex design. The high cost materials used in the conventional sampler holder cell were replaced by stainless steel and conventional ceramics. The sample holder was validated by characterizing yttria-stabilized-zirconia in a temperature range of 25 to 700 ºC. The results do not present variations, discontinuity or unusual noise in the electric signals. Several samples were characterized without maintenance, which demonstrates that the sample holder is electric and mechanic adequate to be used to electrical characterization of ceramics up to 700 ºC.

Spectroscopic characterization of schiff base-copper complexes immobilized in smectite clays

Herein, the immobilization of some Schiff base-copper(II) complexes in smectite clays is described as a strategy for the heterogenization of homogeneous catalysts. The obtained materials were characterized by spectroscopic techniques, mostly UV/Vis, EPR, XANES and luminescence spectroscopy. SWy-2 and synthetic Laponite clays were used for the immobilization of two different complexes that have previously shown catalytic activity in the dismutation of superoxide radicals, and disproportionation of hydrogen peroxide. The obtained results indicated the occurrence of an intriguing intramolecular redox process involving copper and the imine ligand at the surface of the clays. These studies are supported by computational calculations.

A gestão do conhecimento aplicada à reciclagem de componentes automotivos através do tratamento das informações contidas em documentos de patentes

This article evaluates the technologies adopted for recycling and reuse of automobile components, through the analysis of patents documents. The automobile batteries recycling is the main topic, followed by the automatic disassembly of vehicles, tires recycling and polyurethane recycling. None document approached recycling of steel and aluminum or ceramics products. The reduced number of technologies for the recycling of the polymeric compounds (including polyurethane) indicates that a bigger number of research and inventions must be elaborated in the next years, aiming at to the reduction of costs of processes and adequacy to the more restricted environmental legislation.

Composição química da precipitação úmida da região metropolitana de Porto Alegre, Brasil, 2005- 2007

This work aims to quantify the wet precipitation the Metropolitan Area of Porto Alegre (MAPA), in southern Brazil, through the analysis of major ions (by ion chromatography) and metallic elements (ICP/AES). By principal components analysis and cluster analysis was possible to identify the influence of natural and anthropic sources in wet precipitation. The results indicated of the higher contribution to the ions NH4+, SO4(2-) and Ca2+. Thus it was possible to identify the contribution of anthropogenic sources in wet precipitation in the study area, such as power plants, oil refineries, steel and vehicle emissions.

Comparação estrutural entre amostras de materiais tipo hidrotalcita obtidas a partir de diferentes rotas de síntese

Three samples of hydrotalcite-like materials (HTC) were synthesized and their structural characteristics were compared with two HTCs obtained commercially. Thermal analyses, FT-IR, PXRD and textural analyses were used to investigate the structural differences between commercial and synthetic samples. Particularly, the memory effect was observed at temperature higher than 600 ºC. The Rietveld refinements were obtained with expressive accuracy and the statistical parameters of goodness of fit are quite satisfactory. In conclusion, the procedures adopted in synthesis of HTC produced crystalline materials with high surface area materials.

Óxidos de ferro e suas aplicações em processos catalíticos: uma revisão

A review of most of the reported studies on the use of iron oxides as catalyst in specific processes, namely Haber-Bosch reaction, Fischer-Tropsch synthesis, Fenton oxidation and photolytic molecular splitting of water to produce gaseous hydrogen, was carried out. An essential overview is thus presented, intending to address the fundamental meaning, as well as the corresponding chemical mechanisms, and perspectives on new technological potentialities of natural and synthetic iron oxides, more specifically hematite (α-Fe2O3), goethite (α-FeOOH), magnetite (Fe3O4) and maghemite (γ-Fe2O3), in heterogeneous catalysis.

Biossorção passiva de cromo (VI) através da microalga Spirulina platensis

Effluents containing toxic metals are dangerous and more economical, efficient and environmentally friendly treatments must be studied, with the biosorption process with microbial biomass constituting an efficient solution. Thus, the ability of Spirulina platensis biomass for removing chromium (VI) using passive and active biosorption was evaluated. Inactive microalgae biomass and synthetic solution containing chromium (VI) were used to evaluate important factors in the process and biomass biosorption ability. Results of the experiments showed that microalgae have potential for biosorption of chromium (VI), attaining removal of 100.39 mg g-1, and that pH was the variable with the greatest influence on the process.

Química Sem Fronteiras: o desafio da energia

Coal, natural gas and petroleum-based liquid fuels are still the most widely used energy sources in modern society. The current scenario contrasts with the foreseen shortage of petroleum that was spread out in the beginning of the XXI century, when the concept of "energy security" emerged as an urgent agenda to ensure a good balance between energy supply and demand. Much beyond protecting refineries and oil ducts from terrorist attacks, these issues soon developed to a portfolio of measures related to process sustainability, involving at least three fundamental dimensions: (a) the need for technological breakthroughs to improve energy production worldwide; (b) the improvement of energy efficiency in all sectors of modern society; and (c) the increase of the social perception that education is a key-word towards a better use of our energy resources. Together with these technological, economic or social issues, "energy security" is also strongly influenced by environmental issues involving greenhouse gas emissions, loss of biodiversity in environmentally sensitive areas, pollution and poor solid waste management. For these and other reasons, the implementation of more sustainable practices in our currently available industrial facilities and the search for alternative energy sources that could partly replace the fossil fuels became a major priority throughout the world. Regarding fossil fuels, the main technological bottlenecks are related to the exploitation of less accessible petroleum resources such as those in the pre-salt layer, ranging from the proper characterization of these deep-water oil reservoirs, the development of lighter and more efficient equipment for both exploration and exploitation, the optimization of the drilling techniques, the achievement of further improvements in production yields and the establishment of specialized training programs for the technical staff. The production of natural gas from shale is also emerging in several countries but its production in large scale has several problems ranging from the unavoidable environmental impact of shale mining as well as to the bad consequences of its large scale exploitation in the past. The large scale use of coal has similar environmental problems, which are aggravated by difficulties in its proper characterization. Also, the mitigation of harmful gases and particulate matter that are released as a result of combustion is still depending on the development of new gas cleaning technologies including more efficient catalysts to improve its emission profile. On the other hand, biofuels are still struggling to fulfill their role in reducing our high dependence on fossil fuels. Fatty acid alkyl esters (biodiesel) from vegetable oils and ethanol from cane sucrose and corn starch are mature technologies whose market share is partially limited by the availability of their raw materials. For this reason, there has been a great effort to develop "second-generation" technologies to produce methanol, ethanol, butanol, biodiesel, biogas (methane), bio-oils, syngas and synthetic fuels from lower grade renewable feedstocks such as lignocellulosic materials whose consumption would not interfere with the rather sensitive issues of food security. Advanced fermentation processes are envisaged as "third generation" technologies and these are primarily linked to the use of algae feedstocks as well as other organisms that could produce biofuels or simply provide microbial biomass for the processes listed above. Due to the complexity and cost of their production chain, "third generation" technologies usually aim at high value added biofuels such as biojet fuel, biohydrogen and hydrocarbons with a fuel performance similar to diesel or gasoline, situations in which the use of genetically modified organisms is usually required. In general, the main challenges in this field could be summarized as follows: (a) the need for prospecting alternative sources of biomass that are not linked to the food chain; (b) the intensive use of green chemistry principles in our current industrial activities; (c) the development of mature technologies for the production of second and third generation biofuels; (d) the development of safe bioprocesses that are based on environmentally benign microorganisms; (e) the scale-up of potential technologies to a suitable demonstration scale; and (f) the full understanding of the technological and environmental implications of the food vs. fuel debate. On the basis of these, the main objective of this article is to stimulate the discussion and help the decision making regarding "energy security" issues and their challenges for modern society, in such a way to encourage the participation of the Brazilian Chemistry community in the design of a road map for a safer, sustainable and prosper future for our nation.

Explorando produtos naturais microbianos nas fronteiras da Química e da Biologia

The chemistry of natural products has been remarkably growing in the past few decades in Brazil. Aspects related to the isolation and identification of new natural products, as well as their biological activities, have been achieved in different laboratories working on this subject in the country. More recently, the introduction of new molecular biology tools has strongly influenced the research on natural products, mainly those produced by microorganisms, creating new possibilities to assess the chemical diversity of secondary metabolites. This paper describes some ideas on how the research on natural products can have a considerable input from molecular biology in the generation of chemical diversity. We also explore the role of microbial natural products in mediating interspecific interactions and their relevance to ecological studies. Examples of the generation of chemical diversity are highlighted by using genome mining, mutasynthesis, combinatorial biosynthesis, metagenomics, and synthetic biology, while some aspects of microbial ecology are also discussed. The idea to bring up this topic is linked to the remarkable development of molecular biology techniques to generate useful chemicals from different organisms. Here, we focus mainly on microorganisms, even though similar approaches have also been applied to the study of plants and other organisms. Investigations in the frontier of chemistry and biology require interactions between different areas, characterizing the interdisciplinarity of this research field. The necessity of a real integration of chemistry and biology is pivotal to finding correct answers to a number of biological phenomena. The use of molecular biology tools to generate chemical diversity and control biosynthetic pathways is largely explored in the production of important biologically active compounds. Finally, we briefly comment on the Brazilian organization of research in this area, the necessity of new strategies for the graduation programs, and the establishment of networks as a way of organization to overcome some of the problems faced in the area of natural products.

CARACTERIZAÇÃO E ATIVIDADE CATALÍTICA DE K2CO3/AL2O3 NA TRANSESTERIFICAÇÃO DO ÓLEO DE GIRASSOL COM AQUECIMENTO CONVENCIONAL E MICRO-ONDAS

Commercial and synthetic mesoporous aluminas impregnated with potassium carbonate were characterized by X-ray diffraction (XRD), nitrogen physisorption, infrared spectroscopy and 27Al MAS NMR. The activities in the transesterification reaction of sunflower oil with methanol for biodiesel production were evaluated. 27Al MAS NMR spectra evidenced the presence of AlIV and AlVI in the samples, and also of AlV sites in the mesoporous synthesized alumina, which disappeared after impregnation with potassium salt followed by calcination. All aluminas containing potassium were active for biodiesel production from sunflower seed oil, with high conversions by both conventional heating and microwave irradiation.